ASP.NET Core Output Caching: How to Make Web APIs Faster in .NET

ASP.NET Core Output Caching: How to Make Web APIs Faster in .NET When an API receives the same request repeatedly, performing the same database query and rebuilding the same response every time can waste valuable resources. For example, imagine this endpoint: GET /api/products If thousands of users request the same product catalog, your application might repeatedly: HTTP Request ↓ Controller ↓ Database Query ↓ Business Logic ↓ JSON Response For data that doesn't change frequently, this can create unnecessary database load. ASP.NET Core provides Output Caching to help solve this problem. Instead of executing the complete request pipeline every time, the application can temporarily store the generated response and reuse it for subsequent requests. In this tutorial, we'll look at how Output Caching works, how to configure it, how to invalidate cached responses, and when you should avoid using it. What Is Output Caching? Output caching stores the generated response from an endpoint. For example: First request ↓ GET /api/products ↓ Execute controller ↓ Query database ↓ Generate response ↓ Store response in cache Later: Second request ↓ GET /api/products ↓ Cached response ↓ Return immediately The database doesn't need to be queried again while the cached response is valid. Output Caching vs Response Caching These two concepts are often confused. Response Caching Response caching mainly relies on HTTP caching semantics and headers. Output Caching Output caching is controlled by ASP.NET Core and allows your application to decide which responses should be cached and for how long. Output caching provides more control over server-side response caching. 1. Add Output Caching Start by registering the output-cache services. var builder = WebApplication.CreateBuilder(args); builder.Services.AddControllers(); builder.Services.AddOutputCache(); var app = builder.Build(); app.UseOutputCache(); app.MapControllers(); app.Run(); The important pieces are: AddOutputCache() ↓ Configure cac